Positives and Negatives

A linguistics professor was expounding upon the differences in positives and negatives in different languages. According to this professor:

1.) In the English language, a double negative makes something a positive.

2.) In Russian and some related languages, double negative remains a negative.

3.) And the professor asserted there is no language, however, in which a double positive makes a negative.

When he made this last statement someone in the back of the room piped up "Yeah, right."

[ As Read on Car Talk ]